In 1892, Daniels was appointed as assistant professor of political economy, and three years later became a full professor, a post he kept until he entered government service in 1911. He married Joan Robertson in 1898; the two would have a son, Robertson Balfour Daniels. A friend of Wilson's, Daniels joined with Wilson in training the Princeton debaters for their championship matches against Harvard University and Yale University. On May 1, 1911, Daniels became a member of the New Jersey Board of Public Utilities, replacing Frank H. Sommer of Newark, New Jersey. While on the Commission, Daniels authored a rate case opinion involving the Passaic Gas Company, in which he added intangible value for goodwill to the physical value of the corporation. This was controversial, since regulated companies' rates were a percentage of their valuation.
On November 21, 1913, Interstate Commerce CommissionerJohn Hobart Marble died after an attack of acute indigestion. The death of Marble, who had been appointed to fulfill the unexpired term of Franklin Knight Lane after Lane was appointed Interior Secretary, together with the resignation of Charles A. Prouty left Wilson with two seats to fill. He chose Daniels and Henry Clay Hall. While Hall had no difficulty being confirmed, because of the Passaic rate case, Daniels' nomination was bitterly opposed by progressives in the Senate led by Robert M. La Follette, Sr. and New Jersey Senator James Edgar Martine. Wilson refused to withdraw the nominations, stating that he would be personally responsible for Daniels' success as an ICC member. After a three-day battle, the Senate confirmed Daniels, with La Follette himself voting for confirmation. Daniels' confirmation, by a vote of 36 to 27 on April 3, 1914, came after some Democrats who had been inclined to oppose Daniels voted in favor rather than offend President Wilson by rejecting a personal friend of the President. The nomination had been believed to be in serious danger, with the Democrats "in despair" fearing a rejection by the Senate. Wilson's renomination of Daniels in December 1916 set off a second bruising fight in the Senate, with the progressive wing of the Republican party opposing the nomination due to their belief that Daniels was a reactionary. Nonetheless, Daniels was reconfirmed for a full seven-year term on January 10, 1917, 42 to 15.
Later life
In early 1923, nearly a year before the scheduled end of his term, Daniels resigned. He became a professor of transportation at Yale University, where he served until 1940 when he retired. He died January 3, 1944 in Saybrook Point, Connecticut.
